RAYMOND: CORRELATION OF THE ORDOVICIAN STRATA. 253 



Trenton Falls, and zones 2 and 1 of the section below are to be under- 

 stood to be exposed only in small part at Trenton Falls, but com- 

 pletely at Rathbone Brook. The Utica is likewise not exposed directly 

 at Trenton Chasm, but at several places in the immediate vicinity. 



Composite section (Raymond, 112). Zones 7 to 3 and upper part 

 of 2 exposed at Trenton Falls. 



8. Thin-bedded black and brown carbonaceous shale with 

 Triarthnis becki, CryptoUthus tesseUaius, Pleurograptus 

 linearis and many other graptolites. The contact with 

 the limestone below is sharply defined and there are no 

 transition beds. Utica shale (typical). Thickness 

 about 300 feet. 



7. Light gray, coarse-grained lithified coquina in thick beds. 



Rafinesquina deltoidea, Hormotoma trentonensis and other Feet, 

 fossils. 26 



6. Thin-bedded blue limestone with shaly partings. Ra- 

 finesquina deltoidea the common characteristic fossil. 92 



5. Thin-bedded blue limestone with thick shaly partings. 

 Prasopora simidatrix and other common Trenton fossils 

 abundant. 100 



4. Thin- and thick-bedded limestone, dark in color and 

 fine-grained. Diplograptus amplexicaulis a common 

 fossil. 35 



3. Thin-bedded dark limestone with Triplecia extans and 



other fossils. 20 



2. Thin-bedded dark limestone with some inter-bedded 

 coarse-grained layers. CryptoUthus tessellatus the char- 

 acteristic fossil. Trematis terminal is, Platystrophia 

 trentonensis, Calymene senaria and many other fossils 

 present. 41 



1. Thin-bedded gray limestone with an abundance of Dal- 



manella rogata, and some other fossils. ■ 32 



The Leray-Black River is beneath i. I wish to call especial atten- 

 tion to the fact that there are here two zones of CryptoUthus tessella- 

 tus; one in the forty-one feet of limestone near the base of the section 

 (this is the Glens Falls limestone) and one in the Utica shale. 

 CryptoUthus tessellatus is not a facies fossil, as its occurrence in this 

 section shows for it is in both dense fine-grained blue limestone and 

 coarsely crystalline gray limestone (coquina rock) in the lower zone, 

 and in the Utica it is in a very fine-grained carbonaceous shale. In 

 northern New York at the eastern end of Lake Ontario, it is found in 



